Resin composition

ABSTRACT

A resin composition, suitable for moulding by injection, comprises a styrene resin or a polyphenylene ether resin and an amide copolymer having an ester group.

The invention relates to a resin composition, which is suitable forinjection molding, having an excellent abrasion resistance. It comprisesa styrene resin or a polyphenylene ether resin. The invention furtherprovides an article obtained by injection-molding the resin composition.

DESCRIPTION OF PRIOR ARTS

Because of their poor resistance to frictional abrasion, styrene resinsand polyphenylene ether resins have not been applied to parts on whichfrictional abrasion is exerted. Further, when a part must have in partfrictional abrasion resistance for reasons of design, it is strengthenedin part by insert-molding or inserting a small part molded from a resinof good frictional abrasion resistance, such as nylon resin or acetalresin. Further, when frictional abrasion resistance on a flat plane isrequired, this requirement has been met by laminating therewith a sheetor film of a fluorocarbon resin or a nylon resin.

However, although the combined use of such resins is possible when amolded resin article has a simple shape, it is difficult when a moldedresin article has a complicated shape because of difficult assembling ora complicated insert. Thus, the combined use of resins is limited byshapes and requires an increase in the number of steps of manufactureand so has many problems.

It is an object of the present invention to provide a molded article ofgood frictional abrasion resistance without encountering the abovedisadvantages merely by injection-molding a styrene resin or apolyphenylene ether resin.

DESCRIPTION OF THE INVENTION

The invention relates to a resin composition which comprises (1) 100parts by weight of a styrene resin or a polyphenylene ether resin and(2) 0.01 to 50 parts by weight of an ester group-containing amidecopolymer and then an article of the resin composition molded byinjection.

Unlike polyamide, the ester group-containing polyamide copolymer itselfhas a low critical PV value and besides it is not particularly excellentin frictional resistance. Further, unlike silicone oil, carbon, or thelike, the copolymer itself has no lubricating property.

It has been found that a molded article obtained from a materialprepared by mixing such a high-molecular compound with a styrene resinor a polyphenylene ether resin can show a markedly improved frictionalproperty though it is based on the styrene resin or the polyphenyleneether resin.

Examples of the styrene resins used include polystyrene, rubber-modifiedpolystyrene, poly(styrene/acrylonitrile) copolymer and rubber-reinforced(styrene/acrylonitrile) copolymer (ABS resin). A mixture of at least twoof these styrene resins may also be used. Further, those styrene resinswhich are derived by replacing part of the styrene or acrylonitrile inthe above resins with unsaturated monomers copolymerizable with styrene,such as α-methylstyrene, acrylate esters, methacrylate esters andunsaturated dicarboxylic acids or anhydrides thereof, such as maleicacid and maleic anhydride, are also included.

Further a mixture which comprises 50 wt.% or above of the styrene resinand 50 wt.% or below of a thermoplastic resin other than the esterbond-containing polyamide copolymer, such as polycarbonate resin, vinylchloride resin, or polyolefin resin, can also be used as the styreneresin applicable to the present invention.

The polyphenylene ethers used in the present invention are thoseobtained by polycondensing at least one kind of a mononuclear phenolrepresented by general formula (I): ##STR1## (wherein R₁ is a loweralkyl group of 1 to 3 carbon atoms, R₂ and R₃ are each a hydrogen atomor a lower alkyl group of 1 to 3 carbon atoms, and a lower alkylsubstituent must be situated on one or both ortho positions in respectto the hydroxyl group)

and may be homopolymers or copolymers, and include also a graftcopolymer obtained by graft-polymerizing a vinyl aromatic compound witha polyphenylene ether.

Further, the polyphenylene ether resins defined in the present inventioninclude also a composition obtained by mixing said polyphenylene etherwith other resin components.

Examples of the mononuclear phenols represented by general formula (I)include 2,6-dimethylphenol, 2,6-diethylphenol, 2,6-dipropylphenol,2-methyl-6-ethylphenol, 2-methyl-6-propylphenol, 2-ethyl-6-propylphenol,m-cresol, 2,3-dimethylphenol, 2,3-diethylphenol, 2,3-dipropylphenol,2-methyl-3-ethylphenol, 2-methyl-3-propylphenol, 2-ethyl-3-methylphenol,2-ethyl-3-propylphenol, 2-propyl-3-methylphenol, 2-propyl-3-ethylphenol,2,3,6-trimethylphenol, 2,3,6-triethylphenol, 2,3,6-tripropylphenol,2,6-dimethyl-3-ethylphenol, and 2,6-dimethyl-3-propylphenol. Examples ofthe polyphenylene ethers obtained by polycondensing at least one of theabove phenols include poly(2,6-dimethyl-1,4-phenylene)ether,poly(2,6-diethyl-1,4-phenylene)ether,poly(2,6-dipropyl-1,4-phenylene)ether,poly(2-methyl-6-ethyl-1,4-phenylene)ether,poly(2-methyl-6-propyl-1,4-phenylene)ether,poly(2-ethyl-6-propyl-1,4-phenylene)ether,2,6-dimethylphenol/2,3,6-trimethylphenol copolymer,2,6-dimethylphenol/2,3,6-triethylphenol copolymer,2,6-diethylphenol/2,3,6-trimethylphenol copolymer, and2,6-dipropylphenol/2,3,6-trimethylphenol copolymer.

As said other thermoplastic resin components which are mixed with thepolyphenylene ethers, vinyl aromatic resins are suitable. These resinshave at least 25% by weight of monomer structural units represented bygeneral formula (II): ##STR2## (wherein R₄ is a hydrogen atom or a loweralkyl group, z represents a halogen atom or a lower alkyl group, and pis 0 or a positive integer of from 1 to 3)

in the polymer.

Examples of these resins include polystyrene, rubber-reinforcedpolystyrene, poly(styrene/acrylonitrile) copolymer, andrubber-reinforced (styrene/acrylonitrile) copolymer, and further includethose resins derived by replacing part of the styrene or acrylonitrilein the above resins with unsaturated monomers copolymerizable withstyrene, such as α-methylstyrene, acrylate esters, methacrylate esters,unsaturated dicarboxylic acids or anhydrides thereof, and a mixture ofat least two of these may also be used. Further, other thermoplasticresins such as copolymers of diene compounds with vinyl aromaticcompounds, such as polybutadiene and polyisoprene; and elastomers suchas nitrile rubber, ethylene/propylene copolymers,ethylene/propylene/diene copolymers, Thiokol rubbers, polysulfiderubber, acrylic acid rubber, polyurethane, and polyester elastomers arealso applicable to the present invention.

The polyphenylene ether resins (PPE resins) to use in the presentinvention include a poly(2,6-dimethyl-1,4-phenylene)ether, MW of20,000˜150,000, obtained by the so-called oxidative coupling reaction of2,6-dimethylphenol by passing oxygen in the presence of cuprouschloride, or a cocondensed polyphenylene ether obtained by cocondensinga nucleus-substituted phenol such as 2,3,6-trimethylphenol with2,6-dimethylphenol and further includes a PPE resin modified with up to40 wt.% of a polystyrene resin or a rubber-graft polystyrene resin(HI-PS resin) in order to improve the flow of thepoly(2,6-dimethyl-1,4-phenylene)ether or the cocondensed polyphenyleneether. This modification is performed usually by mixing, but graftingmay also be applied.

It is preferable to mix 0.01 to 50 parts by weight, desirably 0.1 to 30parts by weight, more desirably 0.5 to 15 parts by weight of the esterbond-containing polyamide copolymer with 100 parts by weight of thestyrene resin or the polyphenylene ether resin.

When the amount of said polyamide copolymer mixed is smaller than 0.01part by weight per 100 parts by weight of the styrene resin or thepolyphenylene ether resin, the effect of improving frictional abrasionresistance is small. When this amount is larger than 50 parts by weightper 100 parts by weight of the styrene resin or the polyphenylene etherresin, the mechanical strength is decreased, which is not desirable.

The ester bond-containing polyamide copolymers used in the presentinvention are those having ester bonds in a polyamide copolymer. Forexample they are

1. polymers composed of polyamide blocks (a) and polyester blocks (b),and

2. polymers comprising polyamide blocks (a) and polyol blocks (c), bothblocks being linked with each other by an ester bond.

The content of component (a) in said polyamide copolymer is 99 to 10,desirably 90 to 20, more desirably 80 to 30% by weight, based on thetotal copolymer.

When the content of component (a) is higher than 99%, the effect ofimproving abrasion resistance is small, while when it is lower than 10%,the mechanical strength is decreased.

The polyamide block (a) preferably results from a polyamide-formingcompound, that is, an aminocarboxylic acid having 6 to 12 carbon atoms,a lactam having 6 to 12 carbon atoms or a nylon mn salt in which thetotal of m and n is from 12 to 24. In the nylon mn salt, m indicates thediamine portion and n shows the diacid portion.

The polyamide-forming compound is an aminocarboxylic acid such asω-aminocaproic acid, ω-aminoenanthic acid, ω-aminocaprylic acid,ω-aminopelargonic acid, ω-aminocapric acid, 11-aminoundecanoic acid, and12-aminododecanoic acid; lactams such as caprolactam and laurolactam;and nylon mn salts such as nylons 6.6, 6.10, 6.12, 11.6, 11.10, 11.12,12.6, 12.10, and 12.12.

Polyesters (b) mentioned in the present invention include.

(1) polyesters prepared from diacids and diols, and

(2) polycaprolactone-polyesters prepared from ε-caprolactone,ω-hydroxycaproic acid or a C₁ ˜C₃ alkyl ester thereof.

Examples of the polyesters prepared from diacids and diols includepolymer units formed from aromatic dicarboxylic acid components such asphthalic acid, isophthalic acid, terephthalic acid,naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid,diphenyl-4,4'-dicarboxylic acid, and diphenoxyethanedicarboxylic acid;alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid,1,2-cyclohexanedicarboxylic acid, and dicyclohexyl-4,4'-dicarboxylicacid, and aliphatic dicarboxylic acids such as succinic acid, oxalicacid, adipic acid, sebacic acid, and dodecanedioic acid, and diolcomponents such as ethylene glycol, diethylene glycol, triethyleneglycol, tetraethylene glycol, propylene glycol, 1,4-butanediol,1,3-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol,polyethylene glycol, polypropylene glycol, and polytetramethyleneglycol. These ester-forming components can be used alone or in the formof copolymer.

The polycaprolactone polyesters can be obtained, for example, asfollows. Namely, in producing a polycaprolactone polyester bypolymerizing ε-caprolactone, water or a compound having a hydroxyl groupon each end is used as the polymerization initiator.

Examples of the polymerization initiators include resorcinol,pyrocatechol, hydroquinone, pyrogallol, chloroglucinol, benzenetriol,bisphenol-A, bisphenol-F, an ethylene oxide adduct of eachbefore-mentioned compound, dimethylolbenzene, cyclohexanedimethanol,tris(2-hydroxylethyl)isocyanurate, ethylene glycol, diethylene glycol,triethylene glycol, propylene glycol, dipropylene glycol,1,4-butanediol, 1,3-butanediol, 2-methyl-1,3-propylene glycol, neopentylglycol, 1,5-pentanediol, glycerin, trimethylolpropane, 1,6-hexanediol,pentaerythritol, sorbitol, glucose and sucrose. Further the initiatorincludes a polyester-polyol having an average molecular weight of 200 to6,000 which has been formed from a dicarboxylic acid component such asterephthalic acid, isophthalic acid, adipic acid, sebacic acid,undecane-dicarboxylic acid and dodecane-dicarboxylic acid, and a polyolcomponent such as ethylene glycol, diethylene glycol, triethyleneglycol, propylene glycol, 1,4-butanediol, neopentyl glycol,1,5-pentanediol, 1,6-hexanediol, trimethylolpropane, glycerin,pentaerythritol and sorbitol. It moreover includes polyethylene glycol,polytetramethylene glycol, a block or random copolymer of ethylene oxideand propylene oxide, a block or random copolymer of ethylene oxide andtetrahydrofuran, each copolymer having an average molecular weight of200 to 6,000.

The production (polycondensation reaction) of a polyester-polyamidecontaining polyamide blocks (a) and polyester blocks (b) may be carriedout by a usual method. Namely, the polycondensation reaction is carriedout with agitation at a reaction temperature of 220° to 280° C. in ahigh vacuum of below 5 mmHg, desirably below 1 mmHg in the presence of acatalyst.

Although there is a production process in which the polyester blocks arefirst prepared and then converted into a polyester-amide, it is alsopossible that monomers for forming a polyester and monomers for forminga polyamide are fed simultaneously into a polymerization kettle to forma polyester-amide.

In the production of the polyester-amide, a catalyst can give a goodresult. Especially, tetraalkyl titanates such as tetrabutyl titanate andtetramethyl titanate and titanium metal oxalates such as titaniumpotassium oxalate are desirable. In addition, tin compounds such asdibutyltin oxide and dibutyltin laurate and lead compounds such as leadacetate can be mentioned.

In the production of the polyester-amide comprising polyamide blocks andpolyester blocks according to the present invention, the both terminalsof a polyester component may be diols or diacids.

When the both terminals are diols, it is possible to use a dicarboxylicacid of 4 to 36 carbon atoms.

Examples of the dicarboxylic acids of 4 to 36 carbon atoms includearomatic dicarboxylic acids such as phthalic acid, isophthalic acid,terephthalic acid, naphthalene-2,6-dicarboxylic acid,naphthalene-2,7-dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, anddiphenoxyethanedicarboxylic acid, alicyclic dicarboxylic acids such asdicyclohexyl-4,4'-dicarboxylic acid, and aliphatic dicarboxylic acidssuch as succinic acid, oxalic acid, adipic acid, sebacic acid anddodecanedicarboxylic acid. Especially, terephthalic acid isophthalicacid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid anddodecanedicarboxylic acid can be desirably used. A dimer acid may beused for this purpose.

When the both terminals are diacids, diamines are used.

As the diamines, aromatic, alicyclic and aliphatic diamines are used,each preferably having 4 to 36 carbon atoms. Hexamethylenediamine and adimer diamine are most preferable in the aliphatic diamine. In thealicyclic diamine, bis(4,4-aminocyclohexyl)methane, isophorone and 1,3-or 1,4-bis(aminomethyl)cyclohexane are preferable. In the aromaticdiamine, xylenediamine and diaminodiphenylmethane are preferable.

It is also possible in the present invention to replace a part of thepolyester component (b) by a soft component other than a polyester suchas a polyalkylene glycol, for instance, polytetramethylene glycol andpolypropylene glycol, in such an amount that the above discussedadvantages of the invention may be attained.

Examples of polyol blocks (c) in the present invention are polyols of anumber-average molecular weight of 500 to 3000, for example,poly(alkylene oxide)glycols.

Examples of the poly(alkylene oxide)glycols include polyethylene glycol,poly(1,2- or 1,3-propylene oxide)glycol, poly(tetramethyleneoxide)glycol, poly(hexamethylene oxide)glycol, ethylene oxide/propyleneoxide block or random copolymers, and ethylene oxide/tetrahydrofuranblock or random copolymers.

In the polymerization of polyamide blocks (a) with polyol blocks (c),the above-mentioned synthetic process for the polyester-amide isapplicable.

A polymer comprising polyamide blocks (a) and polyol blocks (c), bothblocks having been linked with each other by an ester bond, is called apolyetherester-amide elastomer. It is disclosed in Japanese PatentPublication No. 45419/1981.

In this case, a diacid can be used as a terminal modifier or a molecularweight modifier. As the diacids, those mentioned above can be used.

As mentioned above, the injection-molded resin articles of the presentinvention are effective as molded articles having a sliding section, andexamples of the molded articles having a sliding section includebearings, cams, pistons, hub pullies for VTR cassettes, ratchet gears,small power transmission gears, bushings, switches, control levers ofcar heaters, air conditioners, etc., enclosures of instruments anddevices having a rotary part receiver, recording cassette cases, etc.

It is of course possible to add, if necessary, dispersant, stabilizer,pigment, flame retardant, anti-static agent, and filler or reinforcingagent such as glass fiber to the resin composition used in the presentinvention.

Examples and comparative examples will now be described.

EXAMPLE 1

As the styrene resin used in the experiments, an ABS resin, Trademark"Cevian V #510", a product of Daicel Chemical Industries Ltd., was used,and as the polyphenylene ether resin, a resin "Noryl, grade 731 J" aproduct of EPL Co., was used.

The ester bond-containing polyamide compolymers (A) to (C) were thoseeach prepared from 43, 50, or 74.2% by weight of laurylactam, 45.4, 41,or 21.3% by weight of α,ω-dihydroxy(polytetrahydrofuran) of anumber-average molecular weight of 1000 and 11.6, 9, or 4.5% by weightof dodecanedicarboxylic acid. Ester bond-containing polyamide copolymer(D) was one prepared from 44.7% by weight of 12-aminododecanoic acid,5.3% by weight of dodecanedicarboxylic acid, and 50.0% by weight ofpolycaprolactone-diol of an average molecular weight of 2000.

Ester bond-containing polyamide copolymer (E) was one prepared from44.7% by weight of 12-aminododecanoic acid, 5.3% by weight of adipicacid, and 50.0% by weight of polycaprolactone-diol of anaverage-molecular weight of 2000, and ester bond-containing polyamidecopolymer (F) is one prepared from 46.8% by weight of 12-aminododecanoicacid, 3.4% by weight of adipic acid, and 49.8% by weight of butyleneglycol adipate polyester-diol of an average molecular weight of 2000.

According to the infrared spectrophotometry, each of the polyamidecopolymers (A) to (E) was found to show an absorption peak around 1740cm⁻¹, 1240 cm⁻¹, and 1110 cm⁻¹, so that it was confirmed that thepolyamide copolymers had ester bonds. Absorptions of polyamide segmentsat 1550 cm⁻¹ and 1640 cm⁻¹ were also recognized.

The above listed starting materials were mixed to provide eachcomposition as shown in Tables 1 and 2. Each mixture was kneaded andextruded by an extruder having a diameter of 40 mm and a L/D of 26 toproduced pellets of the resin composition.

The resin composition in the form of pellets was injection-molded by aninjection molding machine, TS-100, a tradename of Nissei Jushi Co., Ltd.Practical abrasion test pieces were molded for use with a Suzukifrictional abrasion tester and had a cylindrical form of an insidediameter of 20 mm φ, an outside diameter of 26 mm φ and a height of 15mm. The condition for molding the test pieces included a cylindertemperature of 225° C. (for a styrene resin) or 260° C. (for apolyphenylene ether resin), a die temperature of 50° C., an injectionpressure of 65 kg/cm² -G, and a cycle of 60 sec. Test pieces for themeasurement of mechanical properties were molded by the same injectionmolding machine under the same molding condition as those used in themolding of the frictional abrasion test pieces.

A frictional abrasion test and a mechanical strength test were carriedout on the test pieces thus obtained.

The frictional abrasion test was performed as follows. A steel testpiece of the same shape as that of the above test piece was set on thelower rotary section of the Suzuki frictional abrasion tester, a moldedtest piece of a resin mixture was set on the upper stationary section,and the measurement was performed without lubrication under a conditionof sliding including a surface pressure of 1 kg/cm², and an averageperipheral speed of 10 m/min. The measurement of mechanical propertieswas made according to the methods of ASTM D638, D790, and D256.

Tables 2 and 4 show the results obtained by the measurement made underthe above conditions.

The specific abrasion loss (mm³ /kg·km) was calculated according to thefollowing equation: ##EQU1##

                                      TABLE 1                                     __________________________________________________________________________                  Examples                     Comparative Examples               Test No.      M - 1                                                                             M - 2                                                                             M - 3                                                                             M - 4                                                                             M - 5                                                                             M - 6                                                                              M - 7                                                                             M - 8                                                                             M - 9                                                                             M - 10                                                                            M -                                                                               M -                __________________________________________________________________________                                                               12                 Cevian #510   100 100 100 100 100 100  100 100 100 100 100 100                Polyamide copolymer (A)                                                                      2   5                                                          Polyamide copolymer (B)                                                                              3   5   10                                             Polyamide copolymer (C)            5                                          Polyamide copolymer (D)                 5                                     Daiamide L-1500                                 5                             Daiamide X-2236                                     5                         Glylucks A-250                                          5                     Novamide ELY                                                5                 __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________                  Examples                    Comparative Examples                Test No.      M - 1                                                                             M - 2                                                                             M - 3                                                                             M - 4                                                                             M - 5                                                                             M - 6                                                                             M - 7                                                                             M - 8                                                                             M - 9                                                                             M - 10                                                                            M -                                                                               M -                 __________________________________________________________________________                                                              12                  Tensile strength kg/cm.sup.2                                                                502 497 493 478 459 498 503 519 516 504 488 511                 Tensile elongation %                                                                        11.0                                                                              11.2                                                                              12.9                                                                              12.6                                                                              5.9 14.1                                                                              8.8 13.7                                                                              13.9                                                                              9.7 11.5                                                                              11.2                Bending strength kg/mm.sup.2                                                                8.45                                                                              7.92                                                                              8.27                                                                              7.97                                                                              7.52                                                                              8.20                                                                              8.24                                                                              8.70                                                                              8.31                                                                              8.38                                                                              8.36                                                                              8.26                Young's modulus in flexure                                                                  275 260 267 259 246 264 261 268 266 264 266 257                 kg/mm.sup.2                                                                   Izod impact strength                                                                        5.5 5.7 6.3 6.4 4.5 4.5 4.6 6.3 2.9 3.7 4.4 3.4                 kg · cm/cm                                                           Coefficient of friction                                                                     0.55                                                                              0.68                                                                              0.59                                                                              0.62                                                                              0.66                                                                              0.66                                                                              0.70                                                                              0.46                                                                              0.53                                                                              0.63                                                                              0.72                                                                              0.73                Specific abrasion loss                                                                      2.43                                                                              0.77                                                                              1.33                                                                              0.64                                                                              0.55                                                                              0.55                                                                              0.23                                                                              6.02                                                                              4.70                                                                              5.85                                                                              5.48                                                                              5.20                mm.sup.3 /kg · km                                                    __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________                 Examples                Comparative Examples                     Test No.     M - 13                                                                            M - 14                                                                            M - 15                                                                            M - 16                                                                            M - 17                                                                            M - 18                                                                            M - 19                                                                            M - 20                                                                            M - 21                                                                            M - 22                                                                            M -                      __________________________________________________________________________                                                         23                       Noryl 731J   100 100 100 100 100 100 100 100 100 100 100                      Polyamide copolymer (B)                                                                     10  5   3   1                                                   Polyamide copolymer (C)       5                                               Polyamide copolymer (D)       5                                               Daiamide L-1500                           5                                   Daiamide X-2236                               5                               Glyluccks A-250                                   5                           Novamide ELY                                          5                       __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________                       Examples                Comparative Examples               Test No.           M - 13                                                                            M - 14                                                                            M - 15                                                                            M - 16                                                                            M - 17                                                                            M - 18                                                                            M - 19                                                                            M - 20                                                                            M - 21                                                                            M -                                                                               M -                __________________________________________________________________________                                                               23                 Tensile strength kg/cm.sup.2                                                                     390 492 500 512 500 494 519 510 505 495 496                Tensile elongation %                                                                             33.5                                                                              34.5                                                                              40.9                                                                              43.1                                                                              42.2                                                                              41.0                                                                              30.8                                                                              35.0                                                                              53.1                                                                              40.8                                                                              39.5               Bending strength kg/mm.sup.2                                                                     7.98                                                                              8.69                                                                              8.86                                                                              8.91                                                                              8.89                                                                              7.90                                                                              9.63                                                                              8.42                                                                              8.29                                                                              7.98                                                                              8.12               Young's modulus in flexure kg/mm.sup.2                                                           205 219 227 231 222 207 241 230 211 205 203                Izod impact strength kg · cm/cm                                                         14.0                                                                              15.3                                                                              15.3                                                                              15.4                                                                              15.3                                                                              14.0                                                                              14.4                                                                              14.0                                                                              14.0                                                                              13.7                                                                              15.2               Coefficient of friction                                                                          0.65                                                                              0.66                                                                              0.67                                                                              0.68                                                                              0.68                                                                              0.68                                                                              0.76                                                                              0.72                                                                              0.68                                                                              0.79                                                                              0.74               Specific abrasion loss mm.sup.3 /kg · km                                                0.27                                                                              0.40                                                                              0.43                                                                              0.42                                                                              0.38                                                                              0.19                                                                              3.12                                                                              2.33                                                                              1.66                                                                              1.73                                                                              2.00               __________________________________________________________________________

COMPARATIVE EXAMPLE 1

As in Example 1, the styrene resin used was an ABS resin, Cevian V 510as tradename, a product of Daicel Chemical Industries Ltd., and thepolyphenylene ether resin used was Noryl 731 J as tradename, a productof EPL Co. Materials added were nylon 12 homopolymer, nylon 12/6copolymer, and polyether-amide elastomer.

The nylon 12 homopolymer and the nylon 12/6 copolymer were "Daiamides"grades L-1500 and X-2236, products of Daicel-Huls, and thepolyether-amide elastomers were Glylucks A-250, a product of DainipponInk & Chemicals, Inc., and Novamide ELY, a product of MitsubishiChemical Industries, Ltd.

When determined by an infrared spectrophotometer, Glylucks A-250 andNovamide ELY showed absorptions at 1110 cm⁻¹ and 1240 cm⁻¹, but did notshow absorption at 1740 cm⁻¹, so that it was confirmed that they werepolyamide polymers free of ester bonds.

The above materials were combined to form compositions, and thesecompositions were measured for frictional abrasion resistance andmechanical properties. The conditions for molding test pieces and theconditions for measurement were the same as those in Example 1.

Tables 1 and 3 show the mixing proportions in the Comparative Example.Tables 2 and 4 show the measurement results in the above case.

When a polyamide-containing polymer which had polyamide blocks but noester bonds was added to a polystyrene resin or a polyphenylene etherresin, any improvement in frictional abrasion resistance could not berealized.

From the results of the present invention, it can be understood that theinjection-molded resin articles obtained according to the presentinvention had a markedly improved specific abrasion loss of 2 mm³ /kg·kmor below.

EXAMPLE 2

Compositions M-24 to M-34 were produced in the same manner as in Example1 and their physical properties were measured.

Tables 5 and 6 show the mixing proportions of the compositions, andTable 7 shows their physical properties.

                  TABLE 5                                                         ______________________________________                                                       Examples                                                       Test No.         M-24       M-25   M-26                                       ______________________________________                                        Cevian #510      100        100    100                                        polyamide copolymer (A)                                                       polyamide copolymer (B)                                                                         1          2                                                polyamide copolymer (C)             2                                         polyamide copolymer (D)                                                       ______________________________________                                    

EXAMPLE 3 AND COMPARATIVE EXAMPLE 2

The polystyrene resins used were as follows. Polystrene, Estyrene G-20as trademark, a product of Shin-Nippon Iron Manufacturing & ChemicalIndustry Co., Ltd., was used as a general-purpose polystyrene, and"Torpolex" grade 850 SE, trademark, a product of Mistui Toatsu ChemicalsInc., was used as a high-impact polystyrene. The resin used was Cevian-N050 SF as tradename, a product of Daicel Chemical Industries Ltd.

Table 8 shows the mixing proportions of the compositions. Table 9 showsthe physical properties of the compositions measured in the same manneras in Example 1.

                  TABLE 6                                                         ______________________________________                                               Examples                                                               Test No. M-27   M-28   M-29 M-30 M-31 M-32 M-33 M-34                          ______________________________________                                        Cevian #510                                                                            100    100    100  100  100  100  100  100                           Polyamide                                                                               10     3      1                                                     (D)                                                                           Polyamide                    10   5    3    1                                 (E)                                                                           Polyamide                                        5                            (F)                                                                           ______________________________________                                    

                                      TABLE 7                                     __________________________________________________________________________              Examples                                                            Test No.  M-24                                                                              M-25                                                                              M-26                                                                              M-27                                                                              M-28                                                                              M-29                                                                              M-30                                                                              M-31                                                                              M-32                                                                              M-33                                                                              M-34                        __________________________________________________________________________    tensile strength                                                                        500 504 511 491 484 490 469 475 496 482 475                         kg/cm.sup.2                                                                   tensile elonga-                                                                         10.5                                                                              10.1                                                                              8.9 10.1                                                                              10.3                                                                              12.7                                                                              9.3 7.5 10.4                                                                              9.1 10.4                        tion %                                                                        bending strength                                                                        8.03                                                                              8.52                                                                              8.58                                                                              7.38                                                                              7.64                                                                              7.87                                                                              6.93                                                                              6.91                                                                              7.85                                                                              7.28                                                                              7.28                        kg/mm.sup.2                                                                   Young's molulus                                                                         270 278 273 232 251 254 229 239 259 249 246                         in flexure kg/mm.sup.2                                                        Izod impact                                                                             5.5 5.4 5.8 9.0 12.4                                                                              13.5                                                                              3.8 3.3 5.2 4.9 9.1                         strength kg · cm/cm                                                  coefficient of                                                                          0.58                                                                              0.53                                                                              0.53                                                                              0.84                                                                              0.73                                                                              0.68                                                                              0.73                                                                              0.63                                                                              0.73                                                                              0.73                                                                              0.73                        friction                                                                      specific abra-                                                                          5.14                                                                              3.54                                                                              5.42                                                                              0.59                                                                              1.05                                                                              3.47                                                                              0.49                                                                              0.58                                                                              0.71                                                                              0.88                                                                              0.72                        sion loss mm.sup.3 /                                                          kg · km                                                              __________________________________________________________________________

                  TABLE 8                                                         ______________________________________                                                                Comparative                                                        Examples   Examples                                              Sample No.     O      P      Q    R    S    T                                 ______________________________________                                        AS resin [Cevian-N]                                                                          100                100                                         050 SF                                                                        polystyrene "Estyrene"                                                                              100              100                                    G-20                                                                          high-impact polystyrene      100            100                               "Torpolex" 850 SE                                                             Polyamide copolymer (B)                                                                       5      5      5                                               ______________________________________                                    

                                      TABLE 9                                     __________________________________________________________________________                                  Comparative                                                       Examples    Examples                                        Sample No.        O   P   Q   R   S    T                                      __________________________________________________________________________    tensile strength kg/cm.sup.2                                                                    724 438 297 729 497  280                                    tensile elongation %                                                                            5.3 3.4 19.1                                                                              4.3 3.4  30.0                                   bending strength kg mm.sup.2                                                                    10.69                                                                             6.74                                                                              4.99                                                                              11.56                                                                             7.12 4.97                                   Young's modulus in flexure kg/mm.sup.2                                                          332 324 185 369 338  197                                    Izod impact strength kg · cm/cm                                                        2.3 2.3 7.6 3.4 2.3  7.5                                    coefficient of friction                                                                         0.79                                                                              0.79                                                                              0.79                                                                              0.79                                                                              1.05 0.79                                   specific abrasion loss mm.sup.3 /kg · km                                               2.71                                                                              9.58                                                                              2.01                                                                              53.3                                                                              1240 32.9                                   __________________________________________________________________________

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A resin compositionsuitable for injection molding, comprising:(1) 100 parts by weight of athermoplastic injection moldable resin component consisting of(a) afirst thermoplastic injection moldable resin selected from the groupconsisting of polystyrene, copolymer of styrene and acrylonitrile andcopolymer of acrylonitrile, butadiene and styrene and (b) up to 50percent by weight of a second thermoplastic injection moldable resindifferent from said first resinand (2) 0.01 to 50 parts by weight of apolyamide block copolymer consisting essentially of(a) 10 to 90 percentby weight of polyamide blocks prepared by polymerizing amino carboxylicacids having 6 to 12 carbon atoms, lactams having 6 to 12 carbon atoms,nylon salts prepared from diamines having from 6 to 12 carbon atoms anddicarboxylic acids having from 6 to 12 carbon atoms, and the balance is(b) polyester blocks or polyol blocks linked to said polyamide blocks byester bonds wherein said second thermoplastic injection moldable resinis different from said polyamide block copolymer.
 2. A resin compositionas claimed in claim 1, in which said polyamide block copolymer comprises(a) a polyamide block and (b) a polyester block.
 3. A resin compositionas claimed in claim 1, in which said polyamide block copolymer comprises(a) a polyamide block and (c) a polyol block, both blocks having beenlinked with each other by an ester group.
 4. A resin composition asclaimed in claim 1, wherein said second resin is selected from the groupconsisting of:polycarbonate resin, vinyl chloride resin and polyolefinresin.
 5. A resin composition as claimed in claim 1, wherein saidaminocarboxylic acids are selected from the group consistingof:ω-aminocaproic acid, ω-aminoenanthic acid, ω-aminocaprylic acid,ω-aminopelargonic acid, ω-aminocapric acid, 11-aminoundecanoic acid and12-aminododecanoic acid, said lactams are selected from the groupconsisting of: caprolactam and laurolactam, and said nylon salts areselected from the group consisting of nylons 6/6, 6/10, 6/12, 11/6,11/10, 11/12, 12/6, 12/10 and 12/12.
 6. A resin composition as claimedin claim 1, wherein said polyester blocks are (a) polyesters preparedfrom diacids and diols, said diacids being selected from the groupconsisting of phthalic acid, isophthalic acid, terephthalic acid,naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid,diphenyl-4,4'-dicarboxylic acid, diphenoxyethanedicarboxylic acid,1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid,dicyclohexyl-4,4'-dicarboxylic acid, succinic acid, oxalic acid, adipicacid, sebacic acid, and dodecanedioic acid, and said diols beingselected from the group consisting of: ethylene glycol, diethyleneglycol, triethylene glycol, tetraethylene glycol, propylene glycol,1,4-butanediol, 1,3-butanediol, neopentyl glycol, 1,5-pentanediol,1,6-hexanediol, polyethylene glycol, polypropylene glycol, andpolytetramethylene glycol, or (b) polycaprolactone-polyesters beingprepared from members of the group consisting of ε-caprolactone,ω-hydroxycaproic acid and C₁ -C₃ alkyl esters thereof, and said polyolblocks being selected from the group consisting of polyols of anumber-average molecular weight of 500-3000, comprising polyethyleneglycol, poly(1,2-propylene oxide)glycol, poly(1,3-propyleneoxide)glycol, poly(tetramethylene oxide)glycol, poly(hexamethyleneoxide)glycol, ethylene oxide/propylene oxide block copolymers, ethyleneoxide/propylene oxide random copolymers, ethylene oxide/tetrahydrofuranblock copolymers and ethylene oxide/tetrahydrofuran random copolymers.7. A resin composition as claimed in claim 1 in which the amount of saidpolyamide block copolymer is from 0.1 to 30 parts by weight.
 8. A resincomposition as claimed in claim 1 in which the amount of said polyamideblock copolymer is from 0.5 to 15 parts by weight.
 9. A resincomposition as claimed in claim 7 in which said polyamide blockcopolymer contains 20 to 90 percent by weight of said polyamide blocks.10. A resin composition as claimed in claim 8 in which said polyamideblock copolymer contains 30 to 80 percent by weight of said polyamideblocks.
 11. A resin composition as claimed in claim 1 in which saidthermoplastic injection moldable resin component consists of a copolymerof acrylonitrile, butadiene and styrene.
 12. A resin composition asclaimed in claim 1, consisting of a mixture of (1) and (2).
 13. Anarticle which has been obtained by injection-moulding the resincomposition as defined in claim 1.